Hot/cold press forming apparatus for thermoformable plastic materials

ABSTRACT

One apparatus for forming a workpiece made of thermoformable plastic material includes: (a) a base member; (b) a positioning wheel or a positioning frame supported by the base member; (c) a suspension tray for supporting a raw workpiece, the suspension tray being supported by the positioning wheel or the positioning frame; (d) a pair of relatively hot dies; (e) a first support arm positioning the hot dies, the first support arm being supported by the base member; (f) a first cylinder mounted on the base member for moving the first support arm whereby the hot dies may be positioned above and below the raw workpiece; (g) a pair of relatively cold dies; (h) a second support arm positioning the cold dies, the second support arm being supported by the base member; (i) a second cylinder mounted on the base for moving the second support arm whereby the set of cold dies may by positioned above and below the workpiece; (j) a press platen; and, (k) a cylinder for moving the press platen whereby the hot dies may be closed upon the workpiece when the pair of hot dies is in position above and below the workpiece and the cold dies may be closed upon the workpiece when the pair of cold dies is in position above and below the workpiece.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to apparatus and methods for forming and shaping aworkpiece made of thermoformable plastic material. The broad term"thermoformable plastic material" is defined to include materials whichcontain thermoplastic resins and thermosetting resins. Thermoplasticresins are defined as materials which have the property of softening orfusing when heated and of hardening and becoming rigid again whencooled. Thermosetting resins are defined as materials which have theproperty of becoming permanently hard and rigid when heated to acritical temperature.

One important type of thermoplastic material is thermoplastic compositematerial. Thermoplastic composite materials are combinations of athermoplastic resin and another material differing in composition orform. The constituents retain their physical identities in the compositematerial, that is, they do not dissolve or otherwise merge completelyinto each other although they act together. Advanced composite materialsare composite materials made by embedding high-strength, high-modulusfibers within an essentially homogeneous matrix. In one particularexample, the invention relates to an apparatus and method for formingand shaping aerospace parts made of advanced thermoplastic compositematerials. Advanced thermoplastic composites are now being employed aslightweight structural materials in many aerospace uses.

(2) Description of the Related Art

Currently, press forming or shaping of parts made of advancedthermoplastic composite materials for aerospace use is generallyaccomplished by heating a pre-consolidated sheet or blank of material inan oven to 750°-800° F. and then transferring it by hand to a press asfast as possible where it is formed between dies before it cools. Thisprocess is difficult, cumbersome, and time-consuming. In many cases, theblank of material will cool below the melting temperature and beginsolidification before the dies can be closed. Forming the part this waywill result in damage to the material. Manual handling of the materialblanks at elevated temperatures (750°-800° F.) requires thickheat-resistant gloves and this makes accurate positioning of the blankin relation to the dies very difficult.

There is also a process for consolidating flat sheets of advancedthermoplastic composites that is known in the art. The process involvesstacking thin layers of flat blanks of thermoplastic composite material.The stack of flat sheets is heated by being placed in a press with hotplatens. The hot material is then transferred by hand to another presswith cold patens where the material is pressed flat and held underpressure until cooled. Here again the problem is that the material coolsrapidly while being moved between presses and, if used to form shapedparts, accurately positioning the hot blanks relative to the dies byhand would be difficult.

SUMMARY OF THE INVENTION

One method of the present invention begins by supporting a raw workpieceon a suspension tray. Then a pair of relatively hot dies is moved intoposition above the workpiece and below the suspension tray. Next therelatively hot dies are closed against the workpiece and the suspensiontray to heat the workpiece and to form and shape the workpiece into thedesired configuration. In one embodiment, a positioning wheel is used torotate the workpiece in relation to the dies while working the workpieceinto its final configuration. Then the relatively hot dies are openedand moved away from the workpiece and the suspension tray. Next a pairof relatively cold dies is moved into position above the workpiece andbelow the suspension tray. Then the relatively cold dies are closedagainst the workpiece and the suspension tray to cool the workpiecewhile maintaining the workpiece in the desired configuration. Finally,the relatively cold dies are opened and the finished workpiece isremoved from the suspension tray.

One apparatus of the present invention includes: (a) a base platen; (b)a positioning wheel supported by the base platen; (c) a suspension trayfor supporting a raw workpiece, the suspension tray being supported bythe positioning wheel; (d) a base member supported on the base platen;(e) a pair of relatively hot dies; (f) a first support arm forsupporting and positioning the relatively hot dies, the first supportarm being supported by the base member; (g) a first cylinder mounted onthe base member for moving the first support arm whereby the relativelyhot dies may be positioned above the raw workpiece and below thesuspension tray; (h) a pair of relatively cold dies; (i) a secondsupport arm for supporting and positioning the relatively cold dies, thesecond support arm being supported by the base member; (j) a secondcylinder mounted on the base member for moving the second support armwhereby the relatively cold dies may be positioned above the workpieceand below the suspension tray; (k) a press platen; and (l) a cylinderfor moving the press platen whereby the relatively hot dies may beclosed upon the raw workpiece and the suspension tray when the pair ofrelatively hot dies is in position above and below the raw workpiece andthe relatively cold dies may be closed upon the workpiece and thesuspension tray when the pair of relatively cold dies is in positionabove and below the workpiece.

Platen and consequent die alignment may be accomplished by usingconventional press tie rods which structurally tie together the pressheadframe and the base platen. However, conventional tie rods are notconsidered essential because die alignment may be accomplished in avariety of ways. Moreover, a variety of press designs can employ theforegoing inventive combination of a pair of relatively hot dies and apair of relatively cold dies in a single press apparatus.

The present invention solves the problems previously existent in thefollowing ways. By placing the raw workpiece material on a suspensiontray, the workpiece can be positioned on a low temperature member thatcan be rotated mechanically in relation to the dies. If needed, a coversheet or film may be placed on top of the workpiece to prevent stickingto the upper hot die. The motion of the suspension tray relative to therelatively hot dies can be sequenced and programmed to form one areabefore another area, similar to hand working. In other cases, pre-pliedstack ups can be formed and consolidated in finished parts saving theexpense of putting the material into pre-consolidated sheet form. Heatis transferred into the raw workpiece by radiation and/or convection bya slow clamping motion. This method enables the press operator to do allof the handling of the material when it is at a low temperature andsolidified, thereby eliminating all the problems of handling a hotlimber material when working thermoplastics. The dies can be moved inand out rapidly without the workpiece being thrown off or out ofposition because the workpiece stays on the suspension tray in thecenter of the press. By using both a relatively hot set and a relativelycold set of dies, the process of heating, forming, and cooling the workmaterial can be speeded up significantly especially when the workpieceis an advanced thermoplastic composite material which has to be heatedto the relatively high temperature of approximately 750° F. Heating aset of dies to this temperature and then cooling the same set of diesagain to room temperature could take several hours. Using separate diesets for heating and cooling enables the heating and cooling process tobe accomplished in a matter of minutes.

Another advantage of the present invention is that high cost diefinishing is not always required because the suspension tray and thecover sheet (if used) contact the workpiece and in doing so impart theirfinish on the workpiece. In this manner, a variety of textures andfinishes can be molded by changing the cover sheet and suspension trayfinish rather than the die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a first embodiment of a hot/cold pressforming apparatus constructed according to the principles of the presentinvention. The press platen and its actuating cylinder and rod are shownin phantom. Conventional press tie rods, which may be employed, are notshown in these drawings.

FIG. 2 is a front elevational view of the inventive apparatus of FIG. 1showing the apparatus in the material load/unload position.

FIG. 3 is a partial vertical sectional view taken along line 3--3 inFIG. 2 showing the positioning wheel and the suspension tray with thesuspension tray supporting a raw workpiece. The press platen and thepressure transfer blocks have been omitted for clarity.

FIG. 4 is an isometric view of a finished thermoformable plasticworkpiece having a Z-shape.

FIG. 5 is a front elevational view of the inventive apparatus of FIG. 1showing the right hand set of dies (the relatively hot dies) in positionabove the workpiece and below the suspension tray before press closing.

FIG. 6 is a front elevational view of the inventive apparatus of FIG. 1showing the press platen down and the relatively hot dies in the closedposition on the workpiece and the suspension tray.

FIG. 7 is a front elevational view of the inventive apparatus of FIG. 1showing the left hand set of dies (the relatively cold dies) in positionabove the workpiece and below the suspension tray before press closing.

FIG. 8 is a front elevational view of the inventive apparatus of FIG. 1showing the press platen down and the relatively cold dies in the closedposition on the workpiece and the suspension tray.

FIG. 9 is a side elevational view of the apparatus of FIG. 5 showing theraw workpiece supported on the suspension tray between the relativelyhot dies with a cover sheet on top of the workpiece to prevent stickingto the upper die. The relatively hot dies are in the open positionbefore press closing. The die mounts are shown in vertical section.

FIG. 10 is a side elevational view of the apparatus of FIG. 6 showingthe workpiece supported on the suspension tray at the point in theforming process when the relatively hot dies are in the fully closedposition and the workpiece has been formed into the desired shape.

FIG. 11 is a side elevational view of the apparatus of FIG. 7 showingthe workpiece supported on the suspension tray between the relativelycold dies. The relatively cold dies are in the open position. The diemounts are shown in vertical section.

FIG. 12 is a side elevational view of the apparatus of FIG. 8 showingthe workpiece supported on the suspension tray between the relativelycold dies which are in the closed position to cool the workpiece.

FIG. 13 is an isometric view of a second embodiment of a hot/cold pressforming apparatus constructed according to the principles of the presentinvention. The press platen and its actuating rod are shown in phantom.

FIG. 14 is a partial vertical sectional view of the apparatus of FIG. 13and shows the positioning posts and the suspension tray with thesuspension tray supporting a raw workpiece. The press platen and thepressure transfer block have been omitted for clarity.

FIG. 15 is an isometric view of a third embodiment of a hot/cold pressforming apparatus constructed according to the principles of the presentinvention. The actuating rod for the press platen is shown in phantom.

FIG. 16 is a front elevational view of the apparatus of FIG. 15 andshows the positioning frame and suspension arms supporting thesuspension tray at a level that gives it clearance for movement abovethe lower dies.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Three apparatus embodiments of the invention will be described first.Referring to the drawings, FIGS. 1 and 2 show the first embodiment of ahot/cold press forming apparatus 20 contructed according to theprinciples of the invention. The terms "hot" and "cold" are used in arelative sense to mean that there exists a temperature differentialbetween the two pairs of forming dies. The apparatus 20 includes a pressplaten 22 which is vertically actuated by a rod 24. Rod 24 is driven bya conventional double-acting cylinder 25 of either the hydraulic orpneumatic type. Cylinder 25 is mounted on a headframe (not shown) or anon-moving structure above press platen 22. Other conventional pressactivating mechanisms may be employed in lieu of the cylinder.

Platen 22 has mounted on its lower face two pressure transfer blocks 26and 28 in a spaced-apart relationship. Pressure transfer blocks 26 and28 are shown as separate members in the drawings, but they may beconstructed in a variety of other ways such as integral parts of platen22. In the center portion of apparatus 20 is a positioning wheel 30, theupper portion of which is located between pressure transfer blocks 26and 28. As shown in FIG. 3, positioning wheel 30 is circular in shapeand its outer periphery carries teeth 32. Teeth 32 engage gears 34 and36 which support positioning wheel 30. Gears 34 and 36 are mounted onbase platen 38.

Base platen 38 may be omitted from the construction of apparatus 20, inwhich event base member 82 may rest directly on the factory floor and bealigned by other means. Gears 34 and 36 may also be mounted on thefactory floor or be mounted on arms extending out from base member 82.Gear 36 is powered by a reversible motor (not shown), so thatpositioning wheel 30 can be rotated in either direction by programmablecontrols or the press operator.

Positioning wheel 30 has four adjustable suspension arms 40a, 40b, 40c,and 40d mounted inside the wheel. The arms include a section constructedof springs 42a, 42b, 42c, and 42d or of an elastic material. The foursuspension arms each have Y-shaped harnesses which are attached to andsupport a suspension tray 44 located at the center of the wheel 30. Asshown in FIGS. 9 and 11 suspension tray 44 is supported at a level thatgives minimum clearance above the lower dies 50 and 76.

As shown in FIGS. 3 and 9, suspension tray 44 supports the raw workpiece46 which is to be formed and shaped by the press. A cover sheet or film47 (FIG. 9) may optionally be used on top of and/or below the workpiece46. Suspension tray 44 is a preformed member, preferably made out ofthin sheet metal (such as aluminum alloy or stainless steel), and havinga shape which is similar to the forming dies. For example, suspensiontray 44, upper hot die 48, and lower hot die 50 may all have a Z-shapein side view as shown in FIG. 9. A thin sheet made in a shape generallyconforming to the die pairs is to be understood by the work "tray" whenused herein. This is the shape of the finished workpiece 52 as shown inFIG. 4. It is to be understood that the Z-shape is shown by way ofexample only and that a variety of other shapes may be used inpracticing the invention. Suspension tray 44 is shown as a solid memberin the drawings but it may be modified to provide for the application ofa vacuum through the suspension tray to hold the workpiece in place.

As shown in FIG. 9, the upper hot die mount 54 and the lower hot diemount 68 have external insulation boards 55 and 69 to insulate the diemounts form the upper hot die 48 and the lower hot die 50, respectively.Upper hot die 48 and lower hot die 50 are heated by heating elements 49and 51, respectively. Dies 48 and 50 each have conventional temperaturegauge and control capabilities such as internal thermocouples (notshown). Upper die mount 54 is attached to the right support arm 58 bymeans of a sliding track 60 as shown in FIG. 1 which has either aspring-driven or a cylinder-driven return so that when platen 22 andpressure transfer blocks 26 and 28 are retracted then upper die mount 54will return to its elevated or open position. The small holes 84 in theside walls of die mounts 54 and 68 are to lighten the weight of the diemounts and to cool them.

Right support arm 58 supports upper hot die mount 54 and is attached tolower hot die mount 68, wherby both move horizontally left and rightwith support arm 58. Lower hot die mount 68 slides horizontally on topof base member 82. A guide or track (not shown) may be used for reducedfriction and better alignment. Lower die mount 68 does not movevertically, whereas upper die mount 54 moves up and down in response toplaten 22 and pressure transfer blocks 26 and 28 when right support arm58 is in the retracted or pressing position (FIGS. 5 and 6). Rightsupport arm 58 is moved horizontally by rod 72 which is driven by adouble-acting cyliner 74 of either the hydraulic or pneumatic typemounted in the right side of base 82 which also supports right supportarm 58.

As shown in FIG. 11, the upper cold die mount 62 and the lower cold diemount 56 have internal cooling elements 63 and 57 for cooling the uppercold die 70 and the lower cold die 76, respectively. Dies 70 and 76 eachhave conventional temperature gauge and control capabilities such asinternal thermocouples (not shown). Upper cold die mount 62 is attachedto the left support arm 64 by means of a sliding track 66 (shown inphantom in FIG. 2) which has either a spring-driven or a cylinder-drivenreturn so that when platen 22 and pressure transfer blocks 26 and 28 areretracted then upper die mount 62 will return to its elevated or openposition. The small holes 86 in the side walls of die mounts 56 and 62are to lighten the weight of the die mounts and to cool them.

Left support arm 64 supports upper cold die mount 62 and is attached tolower cold die mount 56, whereby both move horizontally left and rightwith support arm 64. Lower cold die mount 56 slides horizontally on topof base member 82. A guide or track (not shown) may be used for reducedfriction and better alignment. Lower die mount 56 does not movevertically, whereas upper cold die mount 62 moves up and down inresponse to press platen 22 and pressure transfer blocks 26 and 28 whenleft support arm 64 is in the retracted or pressing position (FIGS. 7and 8). Left support arm 64 is moved horizontally by rod 78 which isdriven by a double-acting cylinder 80 of either the hydraulic orpneumatic type mounted in the left side of base 82 which also supportsleft support arm 64.

Platen alignment, that is, alignment between press platen 22 and baseplaten 38, and consequent die alignment may be accomplished by employingconventional press tie rods which structurally tie together theheadframe (not shown) or some other non-moving structure above pressplaten 22 and the base platen 38. However, conventional tie rods are notconsidered essential because die alignment may be accomplished in otherways. A variety of press designs can employ the foregoing inventioncombination of a pair of relatively hot dies and a pair of relativelycold dies in a single press apparatus.

FIGS. 13 and 14 show the second embodiment of a hot/cold press formingapparatus 90 constructed according to the principles of the invention.The apparatus 90 is a simplified version of the apparatus 20 shown inFIGS. 1 and 2. Components of the two embodiments having like design andconstruction have been given the same reference numerals in thedrawings.

The primary difference between the first and second embodiments is thatpositioning wheel 30 has been replaced by two vertical I-shapedpositioning frames 92 and 94 which are mounted on base member 82a. Eachof the four adjustable suspension arms 96a, 96b, 96c, and 96d have oneend attached to one of the positioning frames 92 or 94 and the other endattached to suspension tray 44 located midway between the positioningframes 92 and 94. Platen 22 has mounted on its lower face a singlepressure transfer block 98. Pressure transfer block 98 is shown as aseparate member in FIG. 13, but it may be constructed as an integralpart of platen 22. Also, in this embodiment, cylinders 74 and 80 may becombined into a single double-acting cylinder with a double-end rod. Inother respects, the construction and operation of apparatus 90 is thesame as apparatus 20. It is to be understood that base platen 38 may beomitted from the construction of apparatus 90 in which event base member82 may rest directly on the factory floor.

FIGS. 15 and 16 show the third embodiment of a hot/cold press formingapparatus 100 constructed according to the principles of the invention.Apparatus 100 is designed for forming and shaping larger workpieces madeof thermoformable plastic material which necessitate the use of largerand heavier dies in the press apparatus. Hence, in this embodiment, thedies are horizontally stationary and the suspension tray and workpiecesare moved horizontally from one set of dies to the other set of dies. Toprevent uneven loading of the press (which is undesirable), a dummyworkpiece moves into position in the unused pair of dies at the sametime that the real workpiece moves into position in the used pair ofdies.

Apparatus 100 has certain components that are the same as in the firstembodiment apparatus 20 shown in FIGS. 1 and 2. Components of the twoembodiments having like design and construction have been given the samereference numerals in the drawings.

In FIGS. 15 and 16, upper hot die 48a and upper cold die 70a are mountedon the lower face of platen 22. A layer of insulation 102 separatesplaten 22 from dies 48a and 70a. Another layer of insulation 104separates dies 48a and 70a from each other.

Lower hot die 50a and lower cold die 76a are mounted on base member 82b.A layer of insulation 106 separates base member 82b from dies 50a and76a. Another layer of insulation 108 separates dies 50a and 76a fromeach other.

Located on the front side of apparatus 100 is a first positioning frame110 having a horizontal member 111 and two vertical T-shaped positioningposts 112 and 114. Horizontal member 111 slides back and forth on top ofbase member 82b. Each of the four adjustable suspension arms 116a, 116b,116c, and 116d have one end attached to one of the vertical positioningposts 112 and 114 and the other end attached to suspension tray 44a. Asecond positioning frame 118 of like design having a horizontal memberand two vertical T-shaped positioning posts is located on the rear sideof apparatus 100. Four more adjustable suspension arms of like designhave one end attached to one of the vertical positioning posts ofpositioning frame 118 and the other end attached to suspension tray 44a.

Positioning frame 110 is moved back and forth in a horizontal plane byrod 130 which is connected through a linkage to horizontal member 111.Rod 130 is driven by a conventional double-acting cylinder 129 mountedon the front side of base member 82b. A second cylinder and rodcombination of identical design is mounted on the rear side of basemember 82b to move positioning frame 118 back and forth in a horizontalplane in tandem with positioning frame 110 so that suspension tray 44ais maintained in correct alignment with the dies. Alternatively, thecylinders can be mounted on the factory floor or some other non-movingstructure. The positioning frames could also be designed as one piecetied together with cross members, and in that event, one cylinder couldbe employed instead of two.

Suspension tray 44a has three work stations 120, 122, and 124. As shownin FIG. 16, a real workpiece 46 is placed on the second work station 122and dummy workpieces 126 and 128 are placed in the first and third workstations 120 and 124, respectively. The dummy workpieces prevent theundesirable situation of uneven loading of the press. When the realworkpiece 46 is being pressed by either the pair of hot dies 48a and 50aor the cold dies 70a and 76a, there is a dummy workpiece of equalthickness being pressed by the other pair of dies.

FIG. 16 also shows that when the dies are in the open positionsuspension tray 44a is held by the suspension arms at a level that givesclearance above the highest portions of lower dies 50a and 76a so thatsuspension tray 44a can move freely back and forth in a horizontal planewithout bumping the lower dies. In other repects, the construction andoperation of apparatus 100 is similar to apparatus 20 described earlier.

The method embodiments of the invention will now be described. Theprocesses begin with the press operator heating the hot dies, such as 48and 50 or 48a and 50a, to the desired temperature. The propertemperature of the hot dies is dependent on the particularthermoformable plastic material that is to be shaped by the apparatus 20or 90 or 100. For example, if the raw workpiece 46 is an advancedthermoplastic composite material, then the temperature needs to berelatively high. To be specific, if the part to be made is an aerospacepart, the raw workpiece 46 may be made of the commercially-availableadvanced thermoplastic composite material known as APC-2 sold byFiberite Corporation. The APC-2 is supplied as a sheet material which iscomposed of continuous carbon fibers dispersed in a matrix of PEEK (apolyetheretherketone of repeating units). To form and shape a workpiecemade of APC-2, the hot dies (48 and 50 or 48a and 50a) should be atabout 750° F.

As another example, if the raw workpiece 46 is made of thecommercially-available thermoplastic composite material known aspolyphenylene sulfide or PPS, then the hot dies should be at about 650°F.

As a further example, if the raw workpiece 46 is made of thecommercially-available thermoplastic composite material known as AZDELsold by PPG Industries Inc., then the hot dies (48 and 50 or 48a and50a) should be at about 450° F. The AZDEL is supplied as a sheetmaterial which is composed of continuous glass fibers dispersed in apolypropylene matrix.

The next step is for the press operator to coat the upper workingsurface of suspension tray 44 or 44a with a conventional mold releaseagent. The workpiece, when molten, will stick to the suspension tray.When the suspension tray cools down, the finished workpiece will bereleased. The operator coats the suspension tray with mold release agentoccasionally during each run. Cover sheet or film 47 (if used) is alsocoated with mold release agent.

The remaining steps in the method using apparatus 20 or 90 will now bedescribed and following that there will be a description of theremaining steps in the method using apparatus 100. While the apparatus20 or 90 is in the material loading position (as shown in FIG. 2 forapparatus 20), the operator places the raw workpiece 46 on top of thesuspension tray 44 as shown in FIGS. 3 and 9. By using cover sheet 47over the workpiece 46 and other forming aids (such as a second piece ofshaped metal above the workpiece), either preconsolidated sheet materialor ply stack ups of thermoplastic composites may be used. Step formingor bump cycles can be used for shaping complex parts or when usingmaterials with outgassing requirements.

For apparatus 20 and 90, the operator then activates cylinder 74 toretract rod 72 as indicated by the arrow in FIG. 5. This moves rightsupport arm 58 horizontally to the left which brings upper hot die mount54 and lower hot die mount 68 within the plane of positioning wheel 30as shown in FIG. 5. Upper hot die mount 54 is now positioned belowpressure transfer blocks 26 and 28 and above suspension tray 44supporting raw workpiece 46 (FIGS. 5 and 9). Lower hot die mount 68 isnow positioned below suspension tray 44.

The operator then activates cylinder 25 which pushes rod 24 verticallydownward as indicated by the upper arrow in FIG. 6. This downwardmovement of press platen 22 and pressure transfer blocks 26 and 28forces down upper hot die mount 60 and upper hot die 48. Heat istransferred to workpiece 46 by radiation and convection from upper hotdie 48 and lower hot die 50. Upper hot die 48 is lowered slowly until ittouches raw workpiece 46 or cover sheet 47 if used. The operator rotatespositioning wheel 30 as needed so that there is maximum contact and heattransfer from upper hot die 48 to the workpiece 46. Suspension tray 44can move slightly up and down and sideways by virtue of the springs orelastic material in the suspension arms. The slow clamping motion ofupper hot die 48 continues until the hot dies 48 and 50 are fully closedas shown in FIGS. 6 and 10. At this point, the workpiece 46 is beingcompression molded. The amount of pressure applied by the hot dies andthe length of time the compression continues are again dependent on theparticular thermoformable plastic material being employed. Withthermoplastic composites, the hot dies are kept fully closed and underpressure for the time period required to completely form and shape theworkpiece into the desired configuration.

The next step is to retract upwardly the press platen 22 and thepressure transfer blocks 26 and 28. Upper hot die mount 54 and upper hotdie 48 return to the open position shown in FIG. 5. Then right supportarm 58 is moved horizontally to the right by extending rod 72. Thismoves the hot dies horizontally to the right and out of the plane ofpositioning wheel 30 and back to the position shown in FIG. 2.

Next the operator activates cylinder 80 to retract rod 78 as indicatedby the arrow in FIG. 7. This moves left support arm 64 horizontally tothe right which brings upper cold die mount 62 and lower cold die mount56 within the plane of positioning wheel 30 as shown in FIG. 7. Uppercold die mount 70 is now positioned below pressure transferred blocks 26and 28 and above suspension tray 44 supporting workpiece 46 (FIGS. 7 and11). Lower cold die mount 56 is now positioned below suspension tray 44.

The operator then activates cylinder 25 which pushes rod 24 verticallydownward as indicated by the upper arrow in FIG. 8. This downwardmovement of press platen 22 and pressure transfer blocks 26 and 28forces down upper cold die mount 62 and upper cold die 70. Upper colddie 70 continues downwardly until the cold dies 70 and 76 are fullyclosed as shown in FIGS. 8 and 12. At this point, the workpiece 46 isbeing compression molded again and simultaneously cooled by the colddies 70 and 76, which may be at room temperature at the beginning. Theamount of pressure applied by the relatively cold dies and the length oftime the compression continues are again dependent on the thermoformableplastic material being employed. For example, when the workpiece is madeof APC-2 to cool to below its glass transition temperature which isabout 290° F. As a further example, when the workpiece is made ofpolyphenylene sulfide the cold dies are held closed and under pressurefor the time required for the polyphenylene sulfide to cool below itsglass transition temperature of about 180° F. Conventional temperaturegauge and control capabilities (not shown) are provided to monitor andmaintain the temperature of each cold die.

The next step is to retract upwardly the press platen 22 and thepressure transfer blocks 26 and 28. Upper cold die mount 62 and uppercold die 70 return to the open position shown in FIG. 7. Then leftsupport arm 64 is moved horizontally to the left by extending rod 78.This moves the cold dies horizontally to the left and out of the planeof positioning wheel 30 and back to the position shown in FIG. 2. Theforegoing processing may also be accomplished automatically by usingprogrammable controls.

The operator then unloads the finished workpiece 52 (FIG. 4) fromsuspension tray 44. The process is then repeated on another rawworkpiece 46 as described above.

The remaining steps in the method of using apparatus 100 will now bedescribed. The operator activates cylinder 25 which pushes rod 24vertically downward. This downward movement of press platen 22 forcesdown the upper dies (upper hot die 48a and upper cold 70a). Heat istransferred to workpiece 46 in the second workstation 122 (FIG. 16) byradiation and convection from upper hot die 48a and lower hot die 50a.Upper hot die 48a is lowered slowly until it touches raw workpiece 46(or cover sheet 47 if used). Suspension tray 44a moves down with theupper dies by virtue of the springs or elastic material in thesuspension arms. The slow clamping motion of upper hot die 48a continuesuntil the hot dies 48a and 50a are closed. At this point, the workpiece46 is being compression molded. The amount of pressure applied by thehot dies and the length of time the compression continues are againdependent on the particular thermoformable plastic material beingemployed. The hot dies are kept closed and under pressure of the timeperiod required to completely form and shape the workpiece into thedesired configuration.

The next step is to retract upwardly the press platen 22. The upper diesreturn to the open position shown in FIG. l6. Then positioning frames110 and 118 are moved horizontally to the left by retracting rod 130into cylinder 129 and likewise for the corresponding cylinder and rod onthe rear side. This moves suspension tray 44a horizontally to the leftand locates workstation 122 and workpiece 46 between upper cold die 70aand lower cold die 76a.

The operator then activates cylinder 25 which pushes rod 24 verticallydownward. This downward movement of press platen 22 forces down uppercold die 70a. Upper cold die 70a continues downwardly until the colddies 70a and 76a are closed. At this point, the workpiece 46 is againbeing compression molded and simultaneously cooled by the cold dies 70aand 76a. The amount of pressure applied by the cold dies and the lengthof time the compression continues are again dependent on thethermoformable plastic material being employed.

The next step is to retract upwardly the press platen 22. The upper diesreturn to the open position. The operator then unloads the finishedworkpiece 52 (FIG. 4) from suspension tray 44a. The process is thenrepeated on another raw workpiece 46 as described above.

A variation of the foregoing processes is usually required when the rawworkpiece 46 is made of a thermosetting material. One example of athermosetting material is the commercially-available thermosettingcomposite material which contains a polyimide resin known as PMR-15.

The following description is presented to exemplify the process forthermosetting materials, such as PMR-15, when using apparatus 20 or 90.The process is similar when using apparatus 100. A raw workpiece 46 madeof PMR-15 composite should be pre-heated in an oven to a temperature ofabout 100°-150° F. The operator then transfers the workpiece 46 to thesuspension tray 44 while the apparatus 20 or 90 is in the materialloading position (as shown in FIG. 2 for apparatus 20). In this case,the cooler dies 70 and 76 additionally have heating elements which areused to pre-heat dies 70 and 76 to an intermediate temperature of about430° F. The cooler dies 70 and 76 are then brought into position aboveand below the workpiece 46 by moving left support arm 64 horizontally tothe right by activating cylinder 80 to retract rod 78 as indicated bythe arrow in FIG. 7.

The operator activates cylinder 25 which pushes rod 24 verticallydownward. The downward movement of press platen 22 forces cooler die 70downward until cooler dies 70 and 76 are closed as shown in FIGS. 8 and12. The workpiece 46 is thus heated to about 430° F. and compressionmolded by dies 70 and 76. This is an important temperature for PMR-15composites because it is the temperature at which the solvent (used tocarry the resin into the fibers) flashes off. The workpiece is allowedto soak at this temperature until the solvent is gone. The operator thenopens the cooler dies 70 and 76 by retracting the press platen 22. Theleft support arm 64 is moved horizontally to the left by extending rod78 in order to move cooler dies 70 and 76 to the left and away from theworkpiece.

The next step is to subject the workpiece to the hotter dies 48 and 50which have been pre-heated to a higher temperature of about 560°-580° F.which is the peak cure temperature for PMR-15 composite. The operatormoves right support arm 58 to the left by activating cylinder 74 toretract rod 72 in order to position the hotter dies 48 and 50 asindicated in FIG. 5. The hotter dies 48 and 50 are then forced down bylowering press platen 22 until the hotter dies 48 and 50 are fullyclosed as shown in FIGS. 6 and 10. At this point, the workpiece 46 isbeing compression molded and cured at about 560°-580° F. The workpieceis held at this temperature for 30 minutes or more for curing.

The next step is to retract the press platen 22 and move right supportarm 58 to the right by extending rod 72 in order to move hotter dies 48and 50 to the right and away from the workpiece. The foregoingprocessing may also be accomplished automatically by using programmablecontrols.

The operator then unloads the finished workpiece 52 from suspension tray44. The process is then repeated on another raw workpiece as describedabove.

As another example, if the raw workpiece 46 is made of thecommercially-available thermoformable plastic material known as TORLONsold by Amoco Chemicals Co., then the cooler dies 70 and 76 should beheated to an intermediate temperature of about 430° F. and the hotterdies 48 and 50 should be heated to a higher temperature of about700°-750° F. TORLON is a poly (amide/imide) material and it is sometimesconsidered to be a thermoplastic material, but for the purposes of thepresent invention it is processed in a manner which is similar to theprocess described above for thermosetting materials.

As will be apparent to those skilled in the art to which the inventionis addressed, the present invention may be embodied in forms other thanthose specifically disclosed above, without departing from the spirit oressential characteristics of the invention. The particular embodimentsof apparatus 20, 90, and 100 described above and the particular detailsof the processes described are therefore to be considered in allrespects as illustrative and not restrictive. The scope of the presentinvention is as set forth in the appended claims rather than beinglimited to the examples of the apparatus 20, 90, and 100 and theprocesses set forth in the foregoing description. Any and allequivalents are intended to be embraced by the claims.

What is claimed is:
 1. An apparatus for forming and shaping a workpiecemade of thermoformable plastic material, which comprises:(a) a basemeans; (b) a positioning means supported by said base means; (c) a traymeans for supporting a raw workpiece, said tray means being supported bysaid positioning means; (d) a first pair of dies; (e) a first supportmeans for supporting said first pair of dies, said first support meansbeing supported by said base means; (f) a first means mounted on saidbase means for moving said first support means whereby said first pairof dies may be positioned above said raw workpiece and below said traymeans; (g) a second pair of dies; (h) a second support means forsupporting said second pair of dies, said second support means beingsupported by said base means; (i) a second means mounted on said basemeans for moving said second support means whereby said second pair ofdies may be positioned above said workpiece and below said tray means;(j) a press platen means; and (k) means for moving said press platenmeans whereby said first pair of dies may be closed against said rawworkpiece and said tray means when said first pair of dies is inposition above and below said workpiece and said second pair of dies maybe closed against said workpiece and said tray means when said secondpair of dies is in position above and below said workpiece.
 2. Theapparatus defined in claim 1 wherein the positioning means comprises awheel-like member and the tray means is supported at the center of saidwheel-like member.
 3. The apparatus defined in claim 2 wherein the outerperiphery of said wheel-like member carries teeth and said teeth engagea pair of gears which support said wheel-like member, whereby saidwheel-like member can be rotated in either direction.
 4. The apparatusdefined in claim 2 wherein the tray means is supported at the center ofsaid wheel-like member by a plurality of suspension means mounted insidethe wheel-like member.
 5. The apparatus defined in claim 1 wherein thepositioning means comprises frame members mounted on said base means andthe tray means is supported midway between said frame members.
 6. Theapparatus defined in claim 1 wherein the tray means is made of metal. 7.The apparatus defined in claim 6 wherein the tray means is made ofaluminum alloy or stainless steel.
 8. An apparatus for forming andshaping a workpiece made of thermoformable plastic material, whichcomprises:(a) a base platen means; (b) a positioning means supported bysaid base platen means; (c) a tray means for supporting a raw workpiece,said tray means being supported by said positioning means; (d) a basemeans supported by said base platen means; (e) a first pair of dies; (f)a first support means for supporting said first pair of dies, said firstsupport means being supported by said base means; (g) a first meansmounted on said base means for moving said first support means wherebysaid first pair of dies may be positioned above said raw workpiece andbelow said tray means; (h) a second pair of dies; (i) a second supportmeans for supporting said second pair of dies, said second support meansbeing supported by said base means; (j) a second means mounted on saidbase means for moving said second support means whereby said second pairof dies may be positioned above said workpiece and below said traymeans; (k) a press platen means; and (l) means for moving said platenmeans whereby said first pair of dies may be closed against said rawworkpiece and said tray means when said first pair of dies is inposition above and below said workpiece and said second pair of dies maybe closed against said workpiece and said tray means when said secondpair of dies is in position above and below workpiece.
 9. The apparatusdefined in claim 8 wherein the positioning means comprises a wheel-likemember and the tray means is supported at the center of said wheel-likemember.
 10. The apparatus defined in claim 9 wherein the outer perimeterof said wheel-like member carries teeth and said teeth engage a pair ofgears which support said wheel-like member, whereby said wheel-likemember can be rotated in either direction.
 11. The apparatus defined inclaim 9 wherein the tray means is supported at the center of saidwheel-like member by a plurality of suspension means mounted inside thewheel-like member.
 12. The apparatus defined in claim 8 wherein the traymeans is made of metal.
 13. The apparatus defined in claim 12 whereinthe tray means is made of aluminum alloy or stainless steel.
 14. Anapparatus for forming and shaping a workpiece made of thermoformableplastic material, which comprise:(a) a base means; (b) a positioningmeans supported by said base means; (c) a tray means for supporting araw workpiece, said tray means being supported by said positioningmeans; (d) a first pair of dies supported by said base means; (e) apress platen means; (f) a second pair of dies mounted on said pressplaten means; (g) actuator means for moving said tray means whereby saidtray means may be moved to a first position and to a second positionbetween said pairs of dies; and (h) means for moving said press platenmeans whereby said first pair of dies and said second pair of dies maybe closed against said raw workpiece and said tray means.
 15. Theapparatus defined in claim 14 wherein the positioning means comprisestwo frame members slidably supported by said base means and the traymeans is supported midway between said frame members.
 16. The apparatusdefined in claim 15 wherein said frame members comprises a horizontalmember and two vertical positioning posts.
 17. The apparatus defined inclaim 14 wherein the tray means is made of metal.
 18. The apparatusdefined in claim 14 wherein the tray means is made of aluminum alloy orstainless steel.
 19. The apparatus defined in claim 14 wherein the traymeans has a plurality of work stations, one of said work stations forsupporting a real workpiece and the remaining work stations forsupporting dummy workpieces.